1. Field of the Invention
This invention relates to a disk player, such as a CD player for reproducing a compact disk (CD) on which digital audio signals are recorded previously. More particularly, it relates to such disk player having the function of detecting the maximum signal level of the digital audio signals recorded on the disk to be reproduced, and a method for detecting the peak signal level.
2. Related Art Statement
In a so-called compact disk CD, on which digital audio signals are recorded, the inner peripheral side of a helical recording track serves as the playback start end, while the outermost peripheral side of the track serves as the playback terminal end. With the usual continuous playback operation, signal reproduction is performed from the center towards the outer periphery of the disk. The program information, recorded on the CD, takes the form of a set of plural program data sections each corresponding to a musical number, and is recorded along with the address information. On the inner peripheral side of the helical recording track, there are recorded data indicating, for example, the number of recorded program data sections or the time required for reproducing the recorded program data sections from the playback start end until the playback terminal end, that is the total playback time, as the table of contents data or TOC data.
In reproducing the CD on which address data are recorded along with the plural program data sections, the playback address data may be utilized to reproduce the CD at a desired position in the program data, that is, to selectively reproduce certain desired program data sections.
Thus, in addition to the usual operational modes for continuous reproduction for sequentially reproducing the plural program data sections recorded on the CD, various other operational modes for reproduction, such as the operational mode for reproducing the program data in an arbitrarily set playing sequence, or the operational mode for reproducing the program data in a random sequence (shuffle mode), are provided in some of the CD players.
These program data reproducing functions of the CD player are utilized for, for example, a dubbing operation in which the record contents of plural disks are selected arbitrarily, the playback sequence is set on a program and the record contents on the disks are selectively reproduced so as to be recorded and edited on the magnetic tape.
On the other hand, with the tape recorder employing a magnetic tape as a recording medium, the signal level of the analog audio signals to be recorded is indicated by level detection/display means, such as peak level meter, and the optimum recording level is set by the user on the basis of the display contents by the level detection display means to effect recording with lesser distortion. The above mentioned optimum recording level is usually set to the maximum signal level of the analog audio signals to be recorded.
Meanwhile, in a disk player for reproducing a digital audio disk, such as a compact disk CD on which digital audio signals are recorded previously the audio data reproduced from the digital audio disk are monitored by, for example, a microcomputer, for detecting the maximum playback output level. However, the digital audio signals recorded on the digital audio disk are the digital data sampled at a sampling frequency high enough to satisfy the Nyguist condition and having a wide dynamic range. For example, in the case of a compact disk (CD), the digital audio signal is the 16-bit digital data having a sampling frequency of 4.1 kHz. For this reason, if the maximum value of the audio data reproduced from the digital audio signals recorded on the digital audio disk is detected directly, an instantaneous peak value, that is, the sound that cannot be sensed by the listener's ears or the instantaneous peak value that cannot be detected or displayed by level detection display means provided in the tape recorder is detected. On the other hand, if the peak value is detected while the audio data are reproduced at a normal playback speed from the digital audio signals recorded on the digital audio disk, the total playback time of the disk would be necessitated for peak detection.
In a disk player in which the digital audio disk, such as a compact disk CD on which the digital audio signals are recorded previously, the maximum playback output level, that is, the data peak value, can be detected by monitoring the audio data reproduced from the digital audio disk by, for example, a microcomputer. However, if the digital audio signals are reproduced at a normal playback speed, the total playback time at the normal reproducing mode of the disk is necessitated to effect the peak detection.
If the total playback time is necessitated for peak detection under the normal playback mode for setting the optimum recording level in the tape recorder, the peak detection efficiency is affected adversely.
On the other hand, in a disk player for reproducing a digital audio disk, such as a compact disk, on which the digital audio signals are recorded previously, the audio data reproduced from the digital audio disk may be monitored such as with a micro-computer, for detecting the maximum playback output level, that is the data peak level. However, if the maximum value of the reproduced audio data of the digital audio signals recorded on the digital audio disk is detected directly, an instantaneous peak value, that is, the sound that cannot be sensed by the listener's ears, or an instantaneous peak value that cannot be detected and displayed by level detection/display means provided in the tape recorder, is detected. If the audio signal in the vicinity of the thus detected peak value is reproduced for setting the recording level for the tape recorder, the recording level cannot be set to an optimum level.